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   1 /*
   2  * Read-Copy Update module-based torture test facility
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright (C) IBM Corporation, 2005, 2006
  19  *
  20  * Authors: Paul E. McKenney <paulmck@us.ibm.com>
  21  *          Josh Triplett <josh@freedesktop.org>
  22  *
  23  * See also:  Documentation/RCU/torture.txt
  24  */
  25 #include <linux/types.h>
  26 #include <linux/kernel.h>
  27 #include <linux/init.h>
  28 #include <linux/module.h>
  29 #include <linux/kthread.h>
  30 #include <linux/err.h>
  31 #include <linux/spinlock.h>
  32 #include <linux/smp.h>
  33 #include <linux/rcupdate.h>
  34 #include <linux/interrupt.h>
  35 #include <linux/sched.h>
  36 #include <asm/atomic.h>
  37 #include <linux/bitops.h>
  38 #include <linux/completion.h>
  39 #include <linux/moduleparam.h>
  40 #include <linux/percpu.h>
  41 #include <linux/notifier.h>
  42 #include <linux/freezer.h>
  43 #include <linux/cpu.h>
  44 #include <linux/delay.h>
  45 #include <linux/byteorder/swabb.h>
  46 #include <linux/stat.h>
  47 #include <linux/srcu.h>
  48 #include <linux/slab.h>
  49
  50 MODULE_LICENSE("GPL");
  51 MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and "
  52               "Josh Triplett <josh@freedesktop.org>");
  53
  54 static int nreaders = -1;       /* # reader threads, defaults to 2*ncpus */
  55 static int nfakewriters = 4;    /* # fake writer threads */
  56 static int stat_interval;       /* Interval between stats, in seconds. */
  57                                 /*  Defaults to "only at end of test". */
  58 static int verbose;             /* Print more debug info. */
  59 static int test_no_idle_hz;     /* Test RCU's support for tickless idle CPUs. */
  60 static int shuffle_interval = 3; /* Interval between shuffles (in sec)*/
  61 static int stutter = 5;         /* Start/stop testing interval (in sec) */
  62 static char *torture_type = "rcu"; /* What RCU implementation to torture. */
  63
  64 module_param(nreaders, int, 0444);
  65 MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
  66 module_param(nfakewriters, int, 0444);
  67 MODULE_PARM_DESC(nfakewriters, "Number of RCU fake writer threads");
  68 module_param(stat_interval, int, 0444);
  69 MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
  70 module_param(verbose, bool, 0444);
  71 MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
  72 module_param(test_no_idle_hz, bool, 0444);
  73 MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
  74 module_param(shuffle_interval, int, 0444);
  75 MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
  76 module_param(stutter, int, 0444);
  77 MODULE_PARM_DESC(stutter, "Number of seconds to run/halt test");
  78 module_param(torture_type, charp, 0444);
  79 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, srcu)");
  80
  81 #define TORTURE_FLAG "-torture:"
  82 #define PRINTK_STRING(s) \
  83         do { printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
  84 #define VERBOSE_PRINTK_STRING(s) \
  85         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
  86 #define VERBOSE_PRINTK_ERRSTRING(s) \
  87         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
  88
  89 static char printk_buf[4096];
  90
  91 static int nrealreaders;
  92 static struct task_struct *writer_task;
  93 static struct task_struct **fakewriter_tasks;
  94 static struct task_struct **reader_tasks;
  95 static struct task_struct *stats_task;
  96 static struct task_struct *shuffler_task;
  97 static struct task_struct *stutter_task;
  98
  99 #define RCU_TORTURE_PIPE_LEN 10
 100
 101 struct rcu_torture {
 102         struct rcu_head rtort_rcu;
 103         int rtort_pipe_count;
 104         struct list_head rtort_free;
 105         int rtort_mbtest;
 106 };
 107
 108 static int fullstop = 0;        /* stop generating callbacks at test end. */
 109 static LIST_HEAD(rcu_torture_freelist);
 110 static struct rcu_torture *rcu_torture_current = NULL;
 111 static long rcu_torture_current_version = 0;
 112 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
 113 static DEFINE_SPINLOCK(rcu_torture_lock);
 114 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
 115         { 0 };
 116 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
 117         { 0 };
 118 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
 119 static atomic_t n_rcu_torture_alloc;
 120 static atomic_t n_rcu_torture_alloc_fail;
 121 static atomic_t n_rcu_torture_free;
 122 static atomic_t n_rcu_torture_mberror;
 123 static atomic_t n_rcu_torture_error;
 124 static struct list_head rcu_torture_removed;
 125
 126 static int stutter_pause_test = 0;
 127
 128 #if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
 129 #define RCUTORTURE_RUNNABLE_INIT 1
 130 #else
 131 #define RCUTORTURE_RUNNABLE_INIT 0
 132 #endif
 133 int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT;
 134
 135 /*
 136  * Allocate an element from the rcu_tortures pool.
 137  */
 138 static struct rcu_torture *
 139 rcu_torture_alloc(void)
 140 {
 141         struct list_head *p;
 142
 143         spin_lock_bh(&rcu_torture_lock);
 144         if (list_empty(&rcu_torture_freelist)) {
 145                 atomic_inc(&n_rcu_torture_alloc_fail);
 146                 spin_unlock_bh(&rcu_torture_lock);
 147                 return NULL;
 148         }
 149         atomic_inc(&n_rcu_torture_alloc);
 150         p = rcu_torture_freelist.next;
 151         list_del_init(p);
 152         spin_unlock_bh(&rcu_torture_lock);
 153         return container_of(p, struct rcu_torture, rtort_free);
 154 }
 155
 156 /*
 157  * Free an element to the rcu_tortures pool.
 158  */
 159 static void
 160 rcu_torture_free(struct rcu_torture *p)
 161 {
 162         atomic_inc(&n_rcu_torture_free);
 163         spin_lock_bh(&rcu_torture_lock);
 164         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
 165         spin_unlock_bh(&rcu_torture_lock);
 166 }
 167
 168 struct rcu_random_state {
 169         unsigned long rrs_state;
 170         long rrs_count;
 171 };
 172
 173 #define RCU_RANDOM_MULT 39916801  /* prime */
 174 #define RCU_RANDOM_ADD  479001701 /* prime */
 175 #define RCU_RANDOM_REFRESH 10000
 176
 177 #define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
 178
 179 /*
 180  * Crude but fast random-number generator.  Uses a linear congruential
 181  * generator, with occasional help from cpu_clock().
 182  */
 183 static unsigned long
 184 rcu_random(struct rcu_random_state *rrsp)
 185 {
 186         if (--rrsp->rrs_count < 0) {
 187                 rrsp->rrs_state +=
 188                         (unsigned long)cpu_clock(raw_smp_processor_id());
 189                 rrsp->rrs_count = RCU_RANDOM_REFRESH;
 190         }
 191         rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
 192         return swahw32(rrsp->rrs_state);
 193 }
 194
 195 static void
 196 rcu_stutter_wait(void)
 197 {
 198         while (stutter_pause_test || !rcutorture_runnable)
 199                 if (rcutorture_runnable)
 200                         schedule_timeout_interruptible(1);
 201                 else
 202                         schedule_timeout_interruptible(HZ);
 203 }
 204
 205 /*
 206  * Operations vector for selecting different types of tests.
 207  */
 208
 209 struct rcu_torture_ops {
 210         void (*init)(void);
 211         void (*cleanup)(void);
 212         int (*readlock)(void);
 213         void (*readdelay)(struct rcu_random_state *rrsp);
 214         void (*readunlock)(int idx);
 215         int (*completed)(void);
 216         void (*deferredfree)(struct rcu_torture *p);
 217         void (*sync)(void);
 218         void (*cb_barrier)(void);
 219         int (*stats)(char *page);
 220         char *name;
 221 };
 222 static struct rcu_torture_ops *cur_ops = NULL;
 223
 224 /*
 225  * Definitions for rcu torture testing.
 226  */
 227
 228 static int rcu_torture_read_lock(void) __acquires(RCU)
 229 {
 230         rcu_read_lock();
 231         return 0;
 232 }
 233
 234 static void rcu_read_delay(struct rcu_random_state *rrsp)
 235 {
 236         long delay;
 237         const long longdelay = 200;
 238
 239         /* We want there to be long-running readers, but not all the time. */
 240
 241         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay);
 242         if (!delay)
 243                 udelay(longdelay);
 244 }
 245
 246 static void rcu_torture_read_unlock(int idx) __releases(RCU)
 247 {
 248         rcu_read_unlock();
 249 }
 250
 251 static int rcu_torture_completed(void)
 252 {
 253         return rcu_batches_completed();
 254 }
 255
 256 static void
 257 rcu_torture_cb(struct rcu_head *p)
 258 {
 259         int i;
 260         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
 261
 262         if (fullstop) {
 263                 /* Test is ending, just drop callbacks on the floor. */
 264                 /* The next initialization will pick up the pieces. */
 265                 return;
 266         }
 267         i = rp->rtort_pipe_count;
 268         if (i > RCU_TORTURE_PIPE_LEN)
 269                 i = RCU_TORTURE_PIPE_LEN;
 270         atomic_inc(&rcu_torture_wcount[i]);
 271         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 272                 rp->rtort_mbtest = 0;
 273                 rcu_torture_free(rp);
 274         } else
 275                 cur_ops->deferredfree(rp);
 276 }
 277
 278 static void rcu_torture_deferred_free(struct rcu_torture *p)
 279 {
 280         call_rcu(&p->rtort_rcu, rcu_torture_cb);
 281 }
 282
 283 static struct rcu_torture_ops rcu_ops = {
 284         .init = NULL,
 285         .cleanup = NULL,
 286         .readlock = rcu_torture_read_lock,
 287         .readdelay = rcu_read_delay,
 288         .readunlock = rcu_torture_read_unlock,
 289         .completed = rcu_torture_completed,
 290         .deferredfree = rcu_torture_deferred_free,
 291         .sync = synchronize_rcu,
 292         .cb_barrier = rcu_barrier,
 293         .stats = NULL,
 294         .name = "rcu"
 295 };
 296
 297 static void rcu_sync_torture_deferred_free(struct rcu_torture *p)
 298 {
 299         int i;
 300         struct rcu_torture *rp;
 301         struct rcu_torture *rp1;
 302
 303         cur_ops->sync();
 304         list_add(&p->rtort_free, &rcu_torture_removed);
 305         list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
 306                 i = rp->rtort_pipe_count;
 307                 if (i > RCU_TORTURE_PIPE_LEN)
 308                         i = RCU_TORTURE_PIPE_LEN;
 309                 atomic_inc(&rcu_torture_wcount[i]);
 310                 if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 311                         rp->rtort_mbtest = 0;
 312                         list_del(&rp->rtort_free);
 313                         rcu_torture_free(rp);
 314                 }
 315         }
 316 }
 317
 318 static void rcu_sync_torture_init(void)
 319 {
 320         INIT_LIST_HEAD(&rcu_torture_removed);
 321 }
 322
 323 static struct rcu_torture_ops rcu_sync_ops = {
 324         .init = rcu_sync_torture_init,
 325         .cleanup = NULL,
 326         .readlock = rcu_torture_read_lock,
 327         .readdelay = rcu_read_delay,
 328         .readunlock = rcu_torture_read_unlock,
 329         .completed = rcu_torture_completed,
 330         .deferredfree = rcu_sync_torture_deferred_free,
 331         .sync = synchronize_rcu,
 332         .cb_barrier = NULL,
 333         .stats = NULL,
 334         .name = "rcu_sync"
 335 };
 336
 337 /*
 338  * Definitions for rcu_bh torture testing.
 339  */
 340
 341 static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
 342 {
 343         rcu_read_lock_bh();
 344         return 0;
 345 }
 346
 347 static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
 348 {
 349         rcu_read_unlock_bh();
 350 }
 351
 352 static int rcu_bh_torture_completed(void)
 353 {
 354         return rcu_batches_completed_bh();
 355 }
 356
 357 static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
 358 {
 359         call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
 360 }
 361
 362 struct rcu_bh_torture_synchronize {
 363         struct rcu_head head;
 364         struct completion completion;
 365 };
 366
 367 static void rcu_bh_torture_wakeme_after_cb(struct rcu_head *head)
 368 {
 369         struct rcu_bh_torture_synchronize *rcu;
 370
 371         rcu = container_of(head, struct rcu_bh_torture_synchronize, head);
 372         complete(&rcu->completion);
 373 }
 374
 375 static void rcu_bh_torture_synchronize(void)
 376 {
 377         struct rcu_bh_torture_synchronize rcu;
 378
 379         init_completion(&rcu.completion);
 380         call_rcu_bh(&rcu.head, rcu_bh_torture_wakeme_after_cb);
 381         wait_for_completion(&rcu.completion);
 382 }
 383
 384 static struct rcu_torture_ops rcu_bh_ops = {
 385         .init = NULL,
 386         .cleanup = NULL,
 387         .readlock = rcu_bh_torture_read_lock,
 388         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
 389         .readunlock = rcu_bh_torture_read_unlock,
 390         .completed = rcu_bh_torture_completed,
 391         .deferredfree = rcu_bh_torture_deferred_free,
 392         .sync = rcu_bh_torture_synchronize,
 393         .cb_barrier = rcu_barrier_bh,
 394         .stats = NULL,
 395         .name = "rcu_bh"
 396 };
 397
 398 static struct rcu_torture_ops rcu_bh_sync_ops = {
 399         .init = rcu_sync_torture_init,
 400         .cleanup = NULL,
 401         .readlock = rcu_bh_torture_read_lock,
 402         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
 403         .readunlock = rcu_bh_torture_read_unlock,
 404         .completed = rcu_bh_torture_completed,
 405         .deferredfree = rcu_sync_torture_deferred_free,
 406         .sync = rcu_bh_torture_synchronize,
 407         .cb_barrier = NULL,
 408         .stats = NULL,
 409         .name = "rcu_bh_sync"
 410 };
 411
 412 /*
 413  * Definitions for srcu torture testing.
 414  */
 415
 416 static struct srcu_struct srcu_ctl;
 417
 418 static void srcu_torture_init(void)
 419 {
 420         init_srcu_struct(&srcu_ctl);
 421         rcu_sync_torture_init();
 422 }
 423
 424 static void srcu_torture_cleanup(void)
 425 {
 426         synchronize_srcu(&srcu_ctl);
 427         cleanup_srcu_struct(&srcu_ctl);
 428 }
 429
 430 static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
 431 {
 432         return srcu_read_lock(&srcu_ctl);
 433 }
 434
 435 static void srcu_read_delay(struct rcu_random_state *rrsp)
 436 {
 437         long delay;
 438         const long uspertick = 1000000 / HZ;
 439         const long longdelay = 10;
 440
 441         /* We want there to be long-running readers, but not all the time. */
 442
 443         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay * uspertick);
 444         if (!delay)
 445                 schedule_timeout_interruptible(longdelay);
 446 }
 447
 448 static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
 449 {
 450         srcu_read_unlock(&srcu_ctl, idx);
 451 }
 452
 453 static int srcu_torture_completed(void)
 454 {
 455         return srcu_batches_completed(&srcu_ctl);
 456 }
 457
 458 static void srcu_torture_synchronize(void)
 459 {
 460         synchronize_srcu(&srcu_ctl);
 461 }
 462
 463 static int srcu_torture_stats(char *page)
 464 {
 465         int cnt = 0;
 466         int cpu;
 467         int idx = srcu_ctl.completed & 0x1;
 468
 469         cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
 470                        torture_type, TORTURE_FLAG, idx);
 471         for_each_possible_cpu(cpu) {
 472                 cnt += sprintf(&page[cnt], " %d(%d,%d)", cpu,
 473                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
 474                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
 475         }
 476         cnt += sprintf(&page[cnt], "\n");
 477         return cnt;
 478 }
 479
 480 static struct rcu_torture_ops srcu_ops = {
 481         .init = srcu_torture_init,
 482         .cleanup = srcu_torture_cleanup,
 483         .readlock = srcu_torture_read_lock,
 484         .readdelay = srcu_read_delay,
 485         .readunlock = srcu_torture_read_unlock,
 486         .completed = srcu_torture_completed,
 487         .deferredfree = rcu_sync_torture_deferred_free,
 488         .sync = srcu_torture_synchronize,
 489         .cb_barrier = NULL,
 490         .stats = srcu_torture_stats,
 491         .name = "srcu"
 492 };
 493
 494 /*
 495  * Definitions for sched torture testing.
 496  */
 497
 498 static int sched_torture_read_lock(void)
 499 {
 500         preempt_disable();
 501         return 0;
 502 }
 503
 504 static void sched_torture_read_unlock(int idx)
 505 {
 506         preempt_enable();
 507 }
 508
 509 static int sched_torture_completed(void)
 510 {
 511         return 0;
 512 }
 513
 514 static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
 515 {
 516         call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
 517 }
 518
 519 static void sched_torture_synchronize(void)
 520 {
 521         synchronize_sched();
 522 }
 523
 524 static struct rcu_torture_ops sched_ops = {
 525         .init = rcu_sync_torture_init,
 526         .cleanup = NULL,
 527         .readlock = sched_torture_read_lock,
 528         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
 529         .readunlock = sched_torture_read_unlock,
 530         .completed = sched_torture_completed,
 531         .deferredfree = rcu_sched_torture_deferred_free,
 532         .sync = sched_torture_synchronize,
 533         .cb_barrier = rcu_barrier_sched,
 534         .stats = NULL,
 535         .name = "sched"
 536 };
 537
 538 static struct rcu_torture_ops sched_ops_sync = {
 539         .init = rcu_sync_torture_init,
 540         .cleanup = NULL,
 541         .readlock = sched_torture_read_lock,
 542         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
 543         .readunlock = sched_torture_read_unlock,
 544         .completed = sched_torture_completed,
 545         .deferredfree = rcu_sync_torture_deferred_free,
 546         .sync = sched_torture_synchronize,
 547         .cb_barrier = NULL,
 548         .stats = NULL,
 549         .name = "sched_sync"
 550 };
 551
 552 /*
 553  * RCU torture writer kthread.  Repeatedly substitutes a new structure
 554  * for that pointed to by rcu_torture_current, freeing the old structure
 555  * after a series of grace periods (the "pipeline").
 556  */
 557 static int
 558 rcu_torture_writer(void *arg)
 559 {
 560         int i;
 561         long oldbatch = rcu_batches_completed();
 562         struct rcu_torture *rp;
 563         struct rcu_torture *old_rp;
 564         static DEFINE_RCU_RANDOM(rand);
 565
 566         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
 567         set_user_nice(current, 19);
 568
 569         do {
 570                 schedule_timeout_uninterruptible(1);
 571                 if ((rp = rcu_torture_alloc()) == NULL)
 572                         continue;
 573                 rp->rtort_pipe_count = 0;
 574                 udelay(rcu_random(&rand) & 0x3ff);
 575                 old_rp = rcu_torture_current;
 576                 rp->rtort_mbtest = 1;
 577                 rcu_assign_pointer(rcu_torture_current, rp);
 578                 smp_wmb();
 579                 if (old_rp) {
 580                         i = old_rp->rtort_pipe_count;
 581                         if (i > RCU_TORTURE_PIPE_LEN)
 582                                 i = RCU_TORTURE_PIPE_LEN;
 583                         atomic_inc(&rcu_torture_wcount[i]);
 584                         old_rp->rtort_pipe_count++;
 585                         cur_ops->deferredfree(old_rp);
 586                 }
 587                 rcu_torture_current_version++;
 588                 oldbatch = cur_ops->completed();
 589                 rcu_stutter_wait();
 590         } while (!kthread_should_stop() && !fullstop);
 591         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
 592         while (!kthread_should_stop())
 593                 schedule_timeout_uninterruptible(1);
 594         return 0;
 595 }
 596
 597 /*
 598  * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
 599  * delay between calls.
 600  */
 601 static int
 602 rcu_torture_fakewriter(void *arg)
 603 {
 604         DEFINE_RCU_RANDOM(rand);
 605
 606         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task started");
 607         set_user_nice(current, 19);
 608
 609         do {
 610                 schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
 611                 udelay(rcu_random(&rand) & 0x3ff);
 612                 cur_ops->sync();
 613                 rcu_stutter_wait();
 614         } while (!kthread_should_stop() && !fullstop);
 615
 616         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
 617         while (!kthread_should_stop())
 618                 schedule_timeout_uninterruptible(1);
 619         return 0;
 620 }
 621
 622 /*
 623  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
 624  * incrementing the corresponding element of the pipeline array.  The
 625  * counter in the element should never be greater than 1, otherwise, the
 626  * RCU implementation is broken.
 627  */
 628 static int
 629 rcu_torture_reader(void *arg)
 630 {
 631         int completed;
 632         int idx;
 633         DEFINE_RCU_RANDOM(rand);
 634         struct rcu_torture *p;
 635         int pipe_count;
 636
 637         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
 638         set_user_nice(current, 19);
 639
 640         do {
 641                 idx = cur_ops->readlock();
 642                 completed = cur_ops->completed();
 643                 p = rcu_dereference(rcu_torture_current);
 644                 if (p == NULL) {
 645                         /* Wait for rcu_torture_writer to get underway */
 646                         cur_ops->readunlock(idx);
 647                         schedule_timeout_interruptible(HZ);
 648                         continue;
 649                 }
 650                 if (p->rtort_mbtest == 0)
 651                         atomic_inc(&n_rcu_torture_mberror);
 652                 cur_ops->readdelay(&rand);
 653                 preempt_disable();
 654                 pipe_count = p->rtort_pipe_count;
 655                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
 656                         /* Should not happen, but... */
 657                         pipe_count = RCU_TORTURE_PIPE_LEN;
 658                 }
 659                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
 660                 completed = cur_ops->completed() - completed;
 661                 if (completed > RCU_TORTURE_PIPE_LEN) {
 662                         /* Should not happen, but... */
 663                         completed = RCU_TORTURE_PIPE_LEN;
 664                 }
 665                 ++__get_cpu_var(rcu_torture_batch)[completed];
 666                 preempt_enable();
 667                 cur_ops->readunlock(idx);
 668                 schedule();
 669                 rcu_stutter_wait();
 670         } while (!kthread_should_stop() && !fullstop);
 671         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
 672         while (!kthread_should_stop())
 673                 schedule_timeout_uninterruptible(1);
 674         return 0;
 675 }
 676
 677 /*
 678  * Create an RCU-torture statistics message in the specified buffer.
 679  */
 680 static int
 681 rcu_torture_printk(char *page)
 682 {
 683         int cnt = 0;
 684         int cpu;
 685         int i;
 686         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 687         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 688
 689         for_each_possible_cpu(cpu) {
 690                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 691                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
 692                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
 693                 }
 694         }
 695         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
 696                 if (pipesummary[i] != 0)
 697                         break;
 698         }
 699         cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
 700         cnt += sprintf(&page[cnt],
 701                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
 702                        "rtmbe: %d",
 703                        rcu_torture_current,
 704                        rcu_torture_current_version,
 705                        list_empty(&rcu_torture_freelist),
 706                        atomic_read(&n_rcu_torture_alloc),
 707                        atomic_read(&n_rcu_torture_alloc_fail),
 708                        atomic_read(&n_rcu_torture_free),
 709                        atomic_read(&n_rcu_torture_mberror));
 710         if (atomic_read(&n_rcu_torture_mberror) != 0)
 711                 cnt += sprintf(&page[cnt], " !!!");
 712         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 713         if (i > 1) {
 714                 cnt += sprintf(&page[cnt], "!!! ");
 715                 atomic_inc(&n_rcu_torture_error);
 716                 WARN_ON_ONCE(1);
 717         }
 718         cnt += sprintf(&page[cnt], "Reader Pipe: ");
 719         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 720                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
 721         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 722         cnt += sprintf(&page[cnt], "Reader Batch: ");
 723         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 724                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
 725         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 726         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
 727         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 728                 cnt += sprintf(&page[cnt], " %d",
 729                                atomic_read(&rcu_torture_wcount[i]));
 730         }
 731         cnt += sprintf(&page[cnt], "\n");
 732         if (cur_ops->stats)
 733                 cnt += cur_ops->stats(&page[cnt]);
 734         return cnt;
 735 }
 736
 737 /*
 738  * Print torture statistics.  Caller must ensure that there is only
 739  * one call to this function at a given time!!!  This is normally
 740  * accomplished by relying on the module system to only have one copy
 741  * of the module loaded, and then by giving the rcu_torture_stats
 742  * kthread full control (or the init/cleanup functions when rcu_torture_stats
 743  * thread is not running).
 744  */
 745 static void
 746 rcu_torture_stats_print(void)
 747 {
 748         int cnt;
 749
 750         cnt = rcu_torture_printk(printk_buf);
 751         printk(KERN_ALERT "%s", printk_buf);
 752 }
 753
 754 /*
 755  * Periodically prints torture statistics, if periodic statistics printing
 756  * was specified via the stat_interval module parameter.
 757  *
 758  * No need to worry about fullstop here, since this one doesn't reference
 759  * volatile state or register callbacks.
 760  */
 761 static int
 762 rcu_torture_stats(void *arg)
 763 {
 764         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
 765         do {
 766                 schedule_timeout_interruptible(stat_interval * HZ);
 767                 rcu_torture_stats_print();
 768         } while (!kthread_should_stop());
 769         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
 770         return 0;
 771 }
 772
 773 static int rcu_idle_cpu;        /* Force all torture tasks off this CPU */
 774
 775 /* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
 776  * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
 777  */
 778 static void rcu_torture_shuffle_tasks(void)
 779 {
 780         cpumask_t tmp_mask;
 781         int i;
 782
 783         cpus_setall(tmp_mask);
 784         get_online_cpus();
 785
 786         /* No point in shuffling if there is only one online CPU (ex: UP) */
 787         if (num_online_cpus() == 1) {
 788                 put_online_cpus();
 789                 return;
 790         }
 791
 792         if (rcu_idle_cpu != -1)
 793                 cpu_clear(rcu_idle_cpu, tmp_mask);
 794
 795         set_cpus_allowed_ptr(current, &tmp_mask);
 796
 797         if (reader_tasks) {
 798                 for (i = 0; i < nrealreaders; i++)
 799                         if (reader_tasks[i])
 800                                 set_cpus_allowed_ptr(reader_tasks[i],
 801                                                      &tmp_mask);
 802         }
 803
 804         if (fakewriter_tasks) {
 805                 for (i = 0; i < nfakewriters; i++)
 806                         if (fakewriter_tasks[i])
 807                                 set_cpus_allowed_ptr(fakewriter_tasks[i],
 808                                                      &tmp_mask);
 809         }
 810
 811         if (writer_task)
 812                 set_cpus_allowed_ptr(writer_task, &tmp_mask);
 813
 814         if (stats_task)
 815                 set_cpus_allowed_ptr(stats_task, &tmp_mask);
 816
 817         if (rcu_idle_cpu == -1)
 818                 rcu_idle_cpu = num_online_cpus() - 1;
 819         else
 820                 rcu_idle_cpu--;
 821
 822         put_online_cpus();
 823 }
 824
 825 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
 826  * system to become idle at a time and cut off its timer ticks. This is meant
 827  * to test the support for such tickless idle CPU in RCU.
 828  */
 829 static int
 830 rcu_torture_shuffle(void *arg)
 831 {
 832         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
 833         do {
 834                 schedule_timeout_interruptible(shuffle_interval * HZ);
 835                 rcu_torture_shuffle_tasks();
 836         } while (!kthread_should_stop());
 837         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
 838         return 0;
 839 }
 840
 841 /* Cause the rcutorture test to "stutter", starting and stopping all
 842  * threads periodically.
 843  */
 844 static int
 845 rcu_torture_stutter(void *arg)
 846 {
 847         VERBOSE_PRINTK_STRING("rcu_torture_stutter task started");
 848         do {
 849                 schedule_timeout_interruptible(stutter * HZ);
 850                 stutter_pause_test = 1;
 851                 if (!kthread_should_stop())
 852                         schedule_timeout_interruptible(stutter * HZ);
 853                 stutter_pause_test = 0;
 854         } while (!kthread_should_stop());
 855         VERBOSE_PRINTK_STRING("rcu_torture_stutter task stopping");
 856         return 0;
 857 }
 858
 859 static inline void
 860 rcu_torture_print_module_parms(char *tag)
 861 {
 862         printk(KERN_ALERT "%s" TORTURE_FLAG
 863                 "--- %s: nreaders=%d nfakewriters=%d "
 864                 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
 865                 "shuffle_interval=%d stutter=%d\n",
 866                 torture_type, tag, nrealreaders, nfakewriters,
 867                 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
 868                 stutter);
 869 }
 870
 871 static void
 872 rcu_torture_cleanup(void)
 873 {
 874         int i;
 875
 876         fullstop = 1;
 877         if (stutter_task) {
 878                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
 879                 kthread_stop(stutter_task);
 880         }
 881         stutter_task = NULL;
 882         if (shuffler_task) {
 883                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
 884                 kthread_stop(shuffler_task);
 885         }
 886         shuffler_task = NULL;
 887
 888         if (writer_task) {
 889                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
 890                 kthread_stop(writer_task);
 891         }
 892         writer_task = NULL;
 893
 894         if (reader_tasks) {
 895                 for (i = 0; i < nrealreaders; i++) {
 896                         if (reader_tasks[i]) {
 897                                 VERBOSE_PRINTK_STRING(
 898                                         "Stopping rcu_torture_reader task");
 899                                 kthread_stop(reader_tasks[i]);
 900                         }
 901                         reader_tasks[i] = NULL;
 902                 }
 903                 kfree(reader_tasks);
 904                 reader_tasks = NULL;
 905         }
 906         rcu_torture_current = NULL;
 907
 908         if (fakewriter_tasks) {
 909                 for (i = 0; i < nfakewriters; i++) {
 910                         if (fakewriter_tasks[i]) {
 911                                 VERBOSE_PRINTK_STRING(
 912                                         "Stopping rcu_torture_fakewriter task");
 913                                 kthread_stop(fakewriter_tasks[i]);
 914                         }
 915                         fakewriter_tasks[i] = NULL;
 916                 }
 917                 kfree(fakewriter_tasks);
 918                 fakewriter_tasks = NULL;
 919         }
 920
 921         if (stats_task) {
 922                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
 923                 kthread_stop(stats_task);
 924         }
 925         stats_task = NULL;
 926
 927         /* Wait for all RCU callbacks to fire.  */
 928
 929         if (cur_ops->cb_barrier != NULL)
 930                 cur_ops->cb_barrier();
 931
 932         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
 933
 934         if (cur_ops->cleanup)
 935                 cur_ops->cleanup();
 936         if (atomic_read(&n_rcu_torture_error))
 937                 rcu_torture_print_module_parms("End of test: FAILURE");
 938         else
 939                 rcu_torture_print_module_parms("End of test: SUCCESS");
 940 }
 941
 942 static int __init
 943 rcu_torture_init(void)
 944 {
 945         int i;
 946         int cpu;
 947         int firsterr = 0;
 948         static struct rcu_torture_ops *torture_ops[] =
 949                 { &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
 950                   &srcu_ops, &sched_ops, &sched_ops_sync, };
 951
 952         /* Process args and tell the world that the torturer is on the job. */
 953         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
 954                 cur_ops = torture_ops[i];
 955                 if (strcmp(torture_type, cur_ops->name) == 0)
 956                         break;
 957         }
 958         if (i == ARRAY_SIZE(torture_ops)) {
 959                 printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
 960                        torture_type);
 961                 return (-EINVAL);
 962         }
 963         if (cur_ops->init)
 964                 cur_ops->init(); /* no "goto unwind" prior to this point!!! */
 965
 966         if (nreaders >= 0)
 967                 nrealreaders = nreaders;
 968         else
 969                 nrealreaders = 2 * num_online_cpus();
 970         rcu_torture_print_module_parms("Start of test");
 971         fullstop = 0;
 972
 973         /* Set up the freelist. */
 974
 975         INIT_LIST_HEAD(&rcu_torture_freelist);
 976         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
 977                 rcu_tortures[i].rtort_mbtest = 0;
 978                 list_add_tail(&rcu_tortures[i].rtort_free,
 979                               &rcu_torture_freelist);
 980         }
 981
 982         /* Initialize the statistics so that each run gets its own numbers. */
 983
 984         rcu_torture_current = NULL;
 985         rcu_torture_current_version = 0;
 986         atomic_set(&n_rcu_torture_alloc, 0);
 987         atomic_set(&n_rcu_torture_alloc_fail, 0);
 988         atomic_set(&n_rcu_torture_free, 0);
 989         atomic_set(&n_rcu_torture_mberror, 0);
 990         atomic_set(&n_rcu_torture_error, 0);
 991         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 992                 atomic_set(&rcu_torture_wcount[i], 0);
 993         for_each_possible_cpu(cpu) {
 994                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 995                         per_cpu(rcu_torture_count, cpu)[i] = 0;
 996                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
 997                 }
 998         }
 999
1000         /* Start up the kthreads. */
1001
1002         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
1003         writer_task = kthread_run(rcu_torture_writer, NULL,
1004                                   "rcu_torture_writer");
1005         if (IS_ERR(writer_task)) {
1006                 firsterr = PTR_ERR(writer_task);
1007                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
1008                 writer_task = NULL;
1009                 goto unwind;
1010         }
1011         fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
1012                                    GFP_KERNEL);
1013         if (fakewriter_tasks == NULL) {
1014                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1015                 firsterr = -ENOMEM;
1016                 goto unwind;
1017         }
1018         for (i = 0; i < nfakewriters; i++) {
1019                 VERBOSE_PRINTK_STRING("Creating rcu_torture_fakewriter task");
1020                 fakewriter_tasks[i] = kthread_run(rcu_torture_fakewriter, NULL,
1021                                                   "rcu_torture_fakewriter");
1022                 if (IS_ERR(fakewriter_tasks[i])) {
1023                         firsterr = PTR_ERR(fakewriter_tasks[i]);
1024                         VERBOSE_PRINTK_ERRSTRING("Failed to create fakewriter");
1025                         fakewriter_tasks[i] = NULL;
1026                         goto unwind;
1027                 }
1028         }
1029         reader_tasks = kzalloc(nrealreaders * sizeof(reader_tasks[0]),
1030                                GFP_KERNEL);
1031         if (reader_tasks == NULL) {
1032                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1033                 firsterr = -ENOMEM;
1034                 goto unwind;
1035         }
1036         for (i = 0; i < nrealreaders; i++) {
1037                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
1038                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
1039                                               "rcu_torture_reader");
1040                 if (IS_ERR(reader_tasks[i])) {
1041                         firsterr = PTR_ERR(reader_tasks[i]);
1042                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
1043                         reader_tasks[i] = NULL;
1044                         goto unwind;
1045                 }
1046         }
1047         if (stat_interval > 0) {
1048                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
1049                 stats_task = kthread_run(rcu_torture_stats, NULL,
1050                                         "rcu_torture_stats");
1051                 if (IS_ERR(stats_task)) {
1052                         firsterr = PTR_ERR(stats_task);
1053                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
1054                         stats_task = NULL;
1055                         goto unwind;
1056                 }
1057         }
1058         if (test_no_idle_hz) {
1059                 rcu_idle_cpu = num_online_cpus() - 1;
1060                 /* Create the shuffler thread */
1061                 shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
1062                                           "rcu_torture_shuffle");
1063                 if (IS_ERR(shuffler_task)) {
1064                         firsterr = PTR_ERR(shuffler_task);
1065                         VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
1066                         shuffler_task = NULL;
1067                         goto unwind;
1068                 }
1069         }
1070         if (stutter < 0)
1071                 stutter = 0;
1072         if (stutter) {
1073                 /* Create the stutter thread */
1074                 stutter_task = kthread_run(rcu_torture_stutter, NULL,
1075                                           "rcu_torture_stutter");
1076                 if (IS_ERR(stutter_task)) {
1077                         firsterr = PTR_ERR(stutter_task);
1078                         VERBOSE_PRINTK_ERRSTRING("Failed to create stutter");
1079                         stutter_task = NULL;
1080                         goto unwind;
1081                 }
1082         }
1083         return 0;
1084
1085 unwind:
1086         rcu_torture_cleanup();
1087         return firsterr;
1088 }
1089
1090 module_init(rcu_torture_init);
1091 module_exit(rcu_torture_cleanup);